Haiti is in the middle of a cholera crisis, and after Hurricane Matthew hit the Caribbean island last week, things are likely to get worse. To try to stem some of the spread of disease, the World Health Organization is sending 1 million doses of a cholera vaccine. Though 1 million doses might sound impressive, it’s still not enough to protect all the Haitians who are at risk of contracting the deadly disease.

Supplies worldwide are severely limited

The WHO isn’t sending more cholera vaccines because supplies worldwide are severely limited. Right now, 2.2 million doses have been stockpiled by worldwide health authorities for an estimated 1.4 billion people who are at risk of cholera. In Haiti alone, 10 million people are at risk, and more than 400 suspected cholera cases have already been reported in the areas most affected by the Hurricane. Because vaccination requires two doses per person, the current worldwide supply can cover only a little over 1 million people. “Supply is still heavily heavily restricted,” says Justin Lessler, an associate professor of epidemiology in the Johns Hopkins Bloomberg School of Public Health. “The people who need cholera vaccine are generally the poorest people. People with money generally have the ability to get clean water, stay away from cholera.”

Until recently, the global public health community was reluctant to use vaccines against cholera. In Haiti itself, where the current outbreak began in 2010, policymakers initially rejected vaccination as a tactic. Six years later, thousands of people have been infected — including more than 700 new cases per week in 2016 — and almost 10,000 have died. Hurricane Matthew is expected to create a spike in the number of cases. “We’ve been encouraging use of the vaccine even before [Hurricane Matthew],” says Helen Matzger, the senior program officer on the Gates Foundation Vaccine Delivery Team. “But if not now, when?”

Cholera is a waterborne disease that causes severe diarrhea. Without treatment, it can kill within hours. Every year, there are 1.3 to 4 million cases of cholera worldwide — and as many as 143,000 deaths — mainly in countries where poor sanitation and a lack of clean water help the disease spread. In Haiti, the epidemic was accidentally started in 2010 by UN peacekeepers who dumped infected sewage into a river.

Back then, there was only one cholera vaccine available, called Dukoral, which had a global supply of only 250,000 doses, according to an Associated Press article at the time. It cost around $6 a dose, and it was mainly used by affluent travelers going to cholera-affected countries. Dukoral, which is still used today, is an oral vaccine and it must be diluted in 150 milliliters of clean water, which makes it hard to use in poor countries or disaster zones. It also comes in two doses, which have to be given one to six weeks apart, which complicates its use further, since people must return for the second dose.

“It just seemed unconscionable.”

So health officials and policymakers decided against a vaccination campaign in Haiti. They were concerned that investing in vaccines would distract from the immediate goal of treating sick patients and from the long-term goal of creating a proper water system and sanitation. Some officials were also concerned that the low number of available doses might trigger riots among people who didn’t get a vaccine, says Louise Ivers, senior health and policy advisor at Partners in Health, a non-profit organization that’s been providing health care in Haiti for more than 20 years. The group called for the use of cholera vaccines soon after the outbreak. The decision to eschew vaccination was criticized by some NGOs and infectious disease experts. “For us and for me, it just seemed unconscionable to have a tool available that wasn’t being used,” says Ivers.

Slowly, the tide began to change. In 2011, the WHO approved a second vaccine, called Shanchol, which also comes in two doses but doesn’t need to be diluted. It’s also cheaper, at just $1.85 a dose as of 2013. So in 2012, in partnership with the Haitian Ministry of Health, Partners in Health and another NGO called Gheskio launched a vaccination campaign in a few towns in Haiti — and showed that the vaccines are effective. “The vaccine campaigns were very successful,” says Ivers.

With requests for cholera vaccines increasing and supplies dwindling, the WHO finally created a stockpile for the vaccines in 2013. Global stockpiles exist for all major vaccines, like smallpox, yellow fever, and influenza; they’re kept for emergency situations, so if an outbreak occurs, we’re ready. In 2013, the WHO invested $2 million for a stockpile of 2 million doses, says Dominique Legros, a cholera expert at the WHO. But the supply shortage is still not resolved.

It’s “a chicken and egg situation.”

It’s “a chicken and egg situation,” several experts say. Before the stockpile was created, about 1.2 million vaccine doses were used over a period of 15 years, Legros says. There was very little demand, so pharmaceutical companies weren’t incentivized to make vaccines. Now, the demand is picking up, but the manufacturers are still behind. The United Nations and WHO have to commit to buying the needed vaccines for the manufacturers to produce them, but to do so they need money. And national governments, international organizations, and NGOs always have competing priorities. “They’re always trying to figure out whether or not this is most cost-effective use of their funds and resources,” Lessler says.

To deal with Haiti’s situation, policymakers are trying to help as many people with as few doses of the vaccines as possible. The WHO is considering giving people only a single dose of the vaccine rather than the regular double dose to cover twice as many people, according to Legros. But that way, vaccinated people will be protected for only six months. (With the double dose, there’s 65 percent protection after five years, Legros says.)

Vaccines are not the only solution to fight cholera

Legros says that vaccines are not the only solution to fight cholera. The most important thing is to build sewage treatment plants, sanitation, and a water system that’s maintained through time, even after natural disasters. That’s how the cholera epidemic was solved in Peru in the 1990s, Legros says. There were no vaccines at the time, but public health officials worked to bring sanitation and inform people about personal hygiene. Cholera was eliminated within 10 years. “The question of the vaccines being available is important but not the only one,” Legros says.

Early this year, the WHO approved a third manufacturer for the cholera vaccines in order to increase the supply on the stockpile. The final goal is to have enough vaccines to deploy in countries like Haiti, while also investing in those longer-term solutions that are key to get rid of the disease. “Cholera vaccine is an important tool and it’s a tool we certainly should be using in Haiti,” Lessler says. “Hopefully at some point we’ll have enough vaccines that we can consider in all similar humanitarian crises.”